The Truth Revealed: Why All Calories Aren’t Equal

For decades, the mantra “calories in, calories out” has dominated the realm of weight management. At the time of “heroin chic” when I was a teenager, I could have told you how many calories there were in an apple, banana, avocado, packet of Walkers crisps and a Pot Noodle. My packed lunch regularly ended up in the bin as I perceived it to be too calorific to counter balance the horse riding and fitness classes I went to with a friend. I don’t miss those days.

As an adult with a research background and interest in food and nutrition and all things bio-hacking, I became very well aware that the calorie mantra that was drilled into us by teen magazines in the 1990s was ridiculous. However, now in my 40s it honestly baffles me how much the language of calories is still discussed.

Research highlights a crucial factor that challenges this oversimplified notion: all calories are not created equal – now repeat that outloud. The traditional calorie-centric approach fails to account for the varying metabolic and physiological effects different foods can have on our bodies. In this article, I delve into the reasons why not all calories are equal and how understanding this concept can profoundly impact our health and well-being.

Macronutrient Composition:

Different macronutrients—carbohydrates, proteins, and fats—behave differently in our bodies. Proteins and carbohydrates provide four calories per gram, while fats provide nine calories per gram. However, beyond the caloric value, the body processes these macronutrients differently, affecting metabolism, satiety, and hormonal responses. Protein, for example, has a higher thermic effect of food, meaning it requires more energy to digest, thus promoting increased calorie expenditure.


The thermogenic effect of food refers to the energy expended during digestion and metabolism. Certain foods, such as high-protein sources, have a higher thermic effect compared to others. This means that the body expends more energy to process and absorb the nutrients, leading to a higher overall calorie burn. In contrast, highly processed foods with refined carbohydrates and added sugars may have a lower thermic effect, resulting in fewer calories burned during digestion.

Satiety and Hunger Regulation:

Not all calories affect our hunger and satiety levels equally. Research shows that different foods can have varying effects on appetite-regulating hormones. For instance, protein-rich foods promote feelings of fullness and reduce subsequent food intake, while high-sugar foods can lead to rapid spikes in blood sugar followed by crashes, triggering hunger and cravings. Thus, the quality and composition of the calories consumed play a crucial role in appetite control and long-term weight management.

Nutrient Density:

Calories from nutrient-dense foods, such as fruits, vegetables, whole grains, and lean proteins, provide more than just energy—they supply essential vitamins, minerals, and antioxidants. These nutrients support overall health, immune function, and cellular repair. On the other hand, empty calories from sugary beverages, processed snacks, and refined carbohydrates offer little to no nutritional value, contributing to nutrient deficiencies and health issues.

Impact on Metabolism and Fat Storage:

Certain foods can influence metabolic rate and fat storage. For example, high glycaemic index carbohydrates, like refined grains and sugary foods, cause rapid spikes in blood sugar, triggering insulin release. Chronically elevated insulin levels can promote fat storage and increase the risk of insulin resistance and metabolic disorders. In contrast, consuming whole foods and sources of healthy fats can promote a balanced insulin response and support a healthier metabolism.

Gut Health and Microbiome:

Emerging research highlights the crucial role of the gut microbiome in our overall health. Different types of food can influence the composition and diversity of gut bacteria. A diet rich in fibre, found in fruits, vegetables, and whole grains, nourishes beneficial bacteria and supports a healthy microbiome. In contrast, a diet high in processed foods and low in fibre can negatively impact gut health, potentially affecting digestion, metabolism, and even mental well-being.

Individual Variations:

Each person’s metabolism and genetic makeup are unique, leading to individual variations in how calories are processed and utilised. Factors like age, sex, body composition, and hormonal balance can influence how the body responds to different foods and calories. This means that the same calorie count can have different effects on weight and health outcomes for different individuals. To top it off, those calorie counts on menus in restaurants are at best a guess, at worse, a total work of fiction!

So what?

Shifting our focus from calorie quantity to the quality and composition of the calories we consume is crucial for optimal long-term health and weight management. Understanding that all calories are not equal empowers us to make informed food choices that prioritise nutrient-dense whole foods, balance macronutrients, and promote satiety, stable blood sugar levels, and a healthy metabolism. By embracing this knowledge, we can optimise our nutrition, support overall well-being, and achieve sustainable, long-term health, rather than short-term weight loss or the perpetuation of the yo-yo diet culture.

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